Method of making iron-copper alloy

ABSTRACT

Iron-copper alloys having finely and uniformly dispersed phase structure in which an iron-rich phase dispersed very finely and uniformly in a copper-rich matrix can now be produced on an industrial scale by the inventive method, in which a consumable electrode composed of an iron or copper pipe filled with a number of iron and copper wires and compacted by pressing, the carbon content of said electrode being limited to less than 0.02 percent by weight of said electrode, is progressively melted submerging the bottom end thereof into a molten slag containing at least one metal fluoride and being placed in a water-cooled metal mold by conducting electric current through said consumable electrode and said molten slag and the melt is cooled and solidified in said water-cooled metal mold.

United States Patent [191 Suzuki et al.

l l METHOD OF MAKING IRON-COPPER ALLOY [75] Inventors: Kenzo Suzuki; Toshio Mizobuchi;

Makoto Kase, all of Kumagaya. Japan [73] Assignee: Riken Piston Ring Kogyo Kabushiki Kaisha, Tokyo, Japan [22 Filed: Aug. 3, 1973 211 Appl. N0.;3s5,40s

[30] Foreign Application Priority Data 3,469,968 9/1969 Snow 75/l(l [ill 3,918,957

[ Nov. 11, 1975 OTHER PUBLICATIONS Duckworth e Hoyle. Electroslag Refining. p, I54 l969),

Primary Erumincr-Peter D. Rosenberg Attorney Age/ii, or Firm-Oldham (S2 Oldham Co.

[57] ABSTRACT lroncopper alloys having finel and uniformly dispersed phase structure in which an iron-rich phase dis persed very finely and uniformly in a copper-rich ma trix can now be produced on an industrial scale by the inventive method, in which a consumable electrode composed of an iron or copper pipe filled with a number of iron and copper wires and compacted by pressing, the carbon content of said electrode being limited to less than 0.02 percent by weight of said electrode. is progressively melted submerging the bottom end thereof into a molten slag containing at least one metal fluoride and being placed in a water-cooled metal mold by conducting electric current through said consumable electrode and said molten slag and the melt is cooled and solidified in said water-cooled metal mold.

4 Claims, 14 Drawing Figures US. Patent Nov. 11, 1975 Sheet 1 of4 3,918,957

Fig. IA

U.S. Patent N0v.11, 1975 Sheet20f4 3,918,957

U.S. Patent Nov. 11, 1975 Sheet 3 of4 3,918,957

Fig-4 Fig.6

U.S. Patent N0v.1l, 1975 Sheet4of4 3,918,957

METHOD OF MAKING IRON-COPPER ALLOY BACKGROUND OF THE INVENTION This invention relates to the method of making ironcopper alloys having finely and uniformly dispersed phase structure and is intended to enable an industrial scale production of such alloys.

As is shown in the phase diagram of Fe-Cu binary system, the alloys containing Cu or Fe beyond limited nar row solid-solution composition ranges has two-phase structure composed of iron-rich body-centered cubic alpha phase and copper-rich face-centered cubic gamma phase. Such Fe-Cu alloy makes a homogenuos solution at a temperature above 1,440C, but when it is cooled to the liquidus temperature, most of iron disolved in the solution abruptly solidifies as primary crystal leaving liquid copper containing a small amount of iron. Therefore, when such alloy is melted and cast in an ingot mold according to conventional methods, re-

markable segregation of iron is unavoidable in the resultant ingots and it has been impossible to produce Fe-Cu alloys of fine and uniform structure on a production scale. Incidentally, it is known that small sized ingots of such alloy can be made, only on laboratory scale, without such a remarkable segregation as it can be cooled and solidified relatively rapidly. However, ingots of any industrial scale, for example, having a diameter of at least 100 mm. and preferably of 200 mm. or over, have not been produced without segregation. Up to now, however, various researches have been conducted on Fe-Cu alloys and it is already known that Fe-Cu alloys having finely and uniformly dispersed phase structure in which iron-rich body-centered cubic alpha phase is dispersed finely and uniformly in copperrich face-centered cubic gamma phase matrix can be worked into sheet, wire or the like, and have highly advantageous characteristics including high tensile strength, high wear resistance, high thermal and electrical conductivities, ferromagnetism, etc. Therefore, it is highly desirable to provide any practical method of making such alloys on an industrial scale.

In this connection, it is known that Fe-Cu alloys of uniform structure can be obtained according to the technique of powder metallurgy, but such technique involves disadvantages in that it is difficult to obtain ingots of any substantial size, that it involves high production cost, and that alloys obtained have not desirable finely dispersed phase structure and exhibit only unsatisfactory characteristics.

SUMMARY OF THE INVENTION In view of the foregoing, the present invention is intended to provide a novel method of making Fe-Cu alloys having finely and uniformly dispersed phase structure, the production of which has previously been regarded to be extremely difficult.

According to the present invention, a novel method of making such alloys is provided, which is characterized in that a consumable electrode is composed of an iron or copper pipe filled with a number of iron and copper wires and compacted by pressing, and the carbon content of which being limited to less than 0.02 percent by weight of the said electrode, is submerged at the bottom end thereof into a molten slag containing at least one of metal fluorides and placed in a water cooled metal mold, and is progressively melted at a high temperature by conducting electric current 2 through said consumable electrode and said molten slag and the melt formed is cooled and solidified progressively in said water-cooled metal mold.

In practice of the present invention, the selection of raw materials for the consumable electrode is one of the important factors in obtaining desirable Fe-Cu alloys.

Electrolytic iron or other high purity iron, it being rather expensive, is usable as an iron raw material for the consumable electrode in the present invention. Common steel or mild steel commercially readily available may be also employed successfully as iron raw material in the present invention.

In case where an element or elements selected, for example, from the group of Al, Ni, Mo, W, Ti, Co, Cr, Mn, P and Be are to be added as additive elements or deoxidizers in minute or limited amounts, they can be used in a form of elements or alloys such as ferroalloys.

These raw materials usually contain various kind of impurities in limited amounts and, among the impurities, carbon has a large influence upon the phase structure of the Fe-Cu alloys obtained. Any carbon content exceeding a predetermined limit range is extremely harmfull in the method of the present invention, making it impossible to obtain Fe-Cu alloys of fine and uniform phase structure.

The present invention will now be described in more detail with reference to the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS In the drawings,

FIGS. 1A, 1B, 1C, ID and 1E represent photographs showing respective microstructures of Fe-Cu alloys ac cording to the present invention; These alloys have basically the same composition but are different in carbon content;

FIG. 2 is a schematic representation diagrammatically showing a consumable electrode melting furnace used to carry out the method of the present invention;

FIG. 3 is a schematical transverse cross-sectional view showing one example of a composite consumable electrode according to the present invention;

FIGS. 4, 5 and 6 represent respective micrographs of a 50% Fe-50% Cu alloy made according to the present invention. (See Example I, below) FIG. 4 showing the microstructure of the alloy as cast (X 100),

FIG. 5 showing the microstructure of as cold-drawn in a cross section transverse to the drawing (X 400); and

FIG. 6 showing the same but in a cross section parallel to the drawing direction X 400 FIG. 7 represents a micrograph of Fe 20% Cu alloy made according to the present invention (X 100);

FIG. 8 represents a micrograph of a Cu l5% Fe alloy as cast (X 400);

Flg. 9 represents a micrograph of the same alloy as in FIG. 8 but in the cold-worked and heat treated (X 400); and FIG. 10 represents a micrograph of a Fe- Cu-AI alloy made according to the present invention.

DESCRIPTION OF THE PREFERED EMBODIMENT In the drawings, FIGS. 1A, 1B, 1C, 1D and 1E show respective microstructures of Fe-Cu alloys made according to the same melting process as in the present invention and having basically the same composition but being different in carbon content to explain the effects of carbon content upon the phase structure of the 3 alloy obtained.

The chemical compositions of the respective alloys are listed below.

4 lengthwise direction in the electrode can be negligible small. Such composite consumable'electrode can be made, for example, by filling iron wires and or copper In the phase structures of FIGS. 1A, 1B, 1C, 1D and 1E, the white region represents a copper-rich face-centered cubic gamma phase and the dark region represents a iron-rich body-centered cubic alpha phase. As apparent from these microstructures, the alpha phase is dispersed more and more coarsely as the carbon content increases, and a phase structure in which the alpha phase is extremely coarse is formed with a carbon content more than in about 0.03 percent.

It will be understood from the foregoing that the carbon content of the consumable electrode used in the inventive method should be limited to 0.02 percent or less and preferably to 0.01 percent or less in order to obtain a Fe-Cu alloy of desirable finely and uniformly dispersed phase structure. And this makes it necessary to select raw materials so as to restrain the overall carbon content of the consumable electrode to less than 0.02 percent. In practice, however, the carbon contained in any copper raw material is usually little enough and so the amount of carbon contained in the consumable electrode depends mainly upon the carbon contained in the iron raw material.

It has been previously known that carbon has a substantial influence upon the phase structure of the Fe-Cu alloy and it is necessary to limit the carbon content to 0.005 percent or less in order to avoid segregation of iron phase. In contrast to this, according to the present invention, the Fe-Cu alloys of fine and uniform phase structure can be obtained with carbon content up to 0.02 percent as will be described hereinafter and this is highly advantageous in practical point of view, because of enabling easy and economical selection of raw materials. This means that common steel or mild steel wires commercially readily usable can be successfully used in the present inventive method. Generally, in the ordinary consumable electrode melting process, the consumable electrode has usually been made by casting the melt prepared in an appropriate melting furnace into an appropriate mold. Such cast electrode can also be used in the present inventive method, but the cast electrode of Fe-Cu alloy is liable to involve some segregation or variation in composition along lengthwise direction thereof which results inevitably in segregation or variation of composition in the ingot obtained. Thus, in order to obtain satisfactory results employing cast electrodes, it is necessary to minimize such segregation or variation of composition especially in longthwise direction of the cast electrode by taking special measures by casting into a small metal mold and cooling rapidly. Under these circumstances, the composite consumable electrode which is composed by combination of iron, copper and other necessary additive materials can be successfully used in the present invention. As will be apparent from the following description, use of such composite consumable electrode is highly desirable as the variation of composition along wires in a pipe of copper or iron and then compressing the composite by forging and, if desired, welding the composites in order to raise its electrical conductivity and strength.

FIG. 3 is a schematical transverse cross-sectional view showing one example of such composite consumable electrodes in the state of not yet compressed. In the figure, 15 indicates an iron pipe filled with iron wires 16 and copper wires 17.

As described above, either a cast or composite consumable electrode can be employed in practicing the present invention, but the carbon content of the electrode should be limited to 0.02 percent or less. Melting of the consumable electrode constitutes the most important stage of the method of the present invention. As described hereinbefore, Fe-Cu alloys have metallographically a tendency to make segregated phase structure, and it is known that even in the molten state the melt is liable to separate into two different liquid phases if the temperature is low and this makes one of the reason why remarkable segregation is liable to occur in the resultant ingot. The present invention proposes, upon the basis of investigations conducted to obtain desirable Fe-Cu alloys to raise the melting temperature to prevent the two phase separation in the molten state and further to cool and solidify as quickly as possible in order to prevent segregation in the ingot obtained.

It has been found that in practice the desirable Fe-Cu alloys can be produced by melting a consumable electrode of the characters described above by submerging the bottom end thereof into a molten slag containing at least one of the metal fluorides and placed in a watercooled metal mold by conducting electric current through said consumable electrode and said molten slag.

A practical application of the method of the present invention will now be described with reference to FIG. 2, in which 11 indicates a water-cooled metal mold which has a water inlet 12 and outlet 13 and is closed at the bottom by a detachable base plate 14. A consumable electrode 1 made of materials described hereinbefore is held upright in the metal mold 11 by an appropriate means not described and electric current is conducted through the electrode 1 and the molten slag 2, where-in the electrode 1 and the base plate 14 are electrically connected to a power source, not shown. The slag 2 is melted and heated to very high temperature by the current and the consumable electrode is melted progressively at its bottom end which is submerged in the slag and a molten pool 5 is formed. And the melt 5 formed in the water-cooled metal mold 11 is progressively cooled and solidified forming an ingot 4.

According to the present invention described above, both melting and solidification processes are performed continuously in an identical water-cooled metal mold 11 and the homogeneous melt formed at a high 5 temperature is cooled and solidifed rapidly enough so that Fe-Cu alloys having finely and uniformly dispersed phase structure can be obtained.

Slag materials usable in the method of the present invention include metal fluorides such as CaF MgF and BaF and, if desired, auxiliary ingredients or additives such as metal oxides including A1 M 0 and CaO. The slag serves a very important role in the method of the present invention. In general, desirable Fe-Cu alloys of fine and uniform phase structure can not be obtained only by melting of the consumable electrode usable in the present inventive method according to the conventional vacuum arc-melting process. This means that the use of slag, particularty of that containing a metal fluoride or fluorides is one of the requisit conditions for formation of a desirable phase structure. It is supposed that the current flowing through the molten slag reduces the metal fluoride contained in the slag to provide an appropriate amount of Ca, Mg, etc., which serve as the fine crystal nuclei for the solidification of primary crystals and serve to make the phase structure of the resultant ingot fine and uniform. A few examples of the practical applications of the present invention will next be described.

EXAMPLE 1 50% Fe 50% Cu alloy Steel wires and copper wires of 3 mm. diameter were filled in a steel pipe of 48 mm. outer diameter, 4 mm. thickness and 1.5 meters length to form a long composite of 50% Fe 50% Cu by weight and such a composite was compacted by pressing. A number of such compacted composites were welded together to form a consumable electrode of a substantial length and cross-section. The carbon content of the steel material used was 0.012 percent and that of the obtained consumable electrode averaged 0.0062 percent.

The consumable electrode was progressively melted by submerging the bottom end thereof into a slag contained in a water-cooled metal mold by conducting electric current through said consumable electrode and said slag.

The melting conditions and the chemical composition of the alloy obtained were as follows:

1 Melting conditions Slag Dia. of Consumable Voltage Current composition mold electrode 40 V 5500 A CaF, 80% 120 mm. 70mm X 50mm MgF, 20% x Length 2. Chemical composition of the alloy produced (weight Cu Mn Si S C P Fe 49.4 0.08 0.012 0.008 0.0054 0.004

Bal

3. Specific resistance p= 6.09 pfl-cm 4. Magnetic properties Material flux density in gauss* B 50 B l B 200 As cast 1500 2700 4200 Wire of 2.0 mm dia. hot-drawn 7600 9100 9650 and heat-treated B50, B100 and 8200 represent flux densities in field of 50, 100 and 200 Oe respectively.

5. Mechanical properties Material Tensile strength Elongation Hardness ltg/mm 7: HRB Annealed 59.8 16.5 65 Worked with 63.0 5.2 72 15% reduction Worked with 72.5 2.5 77 50% reduction FIG. 4 represents the microstructure of the alloy obtained as cast condition. FIGS. 5 and 6 illustrate the microstructure of the alloy obtained after hotand colddrawing, in a cross-section transverse to the working direction and in a section paralell thereto respectively. As observed in FlGS. 4, 5 and 6, the alloy obtained had a fine and unifonn dispersed phase structure and the fibrous structure formed by hotor cold-working did not disappear even after heat-treatment.

EXAM PLE 2 Cu 15% Fe alloy A composite consumable electrode of composition 85% Cu 15% Fe was formed by combining steel pipes with copper and steel wires as in the example 1. The carbon content of the consumable electrode obtained was 0.0042 percent. The consumable electrode was melted by a similar process as in the example 1. The melting conditions and the properties of the alloy obtained were as follows.

then aging The microstructures of the alloy obtained are shown in FIG. 8 and FIG. 9. FIG. 8 illustrates the microstructure of the alloy as cast and FIG. 9 illustrates that of the alloy cold-worked and heat-treated.

As apparent from the above, the alloy is excellent in electric conductivity as well as having good mechanical properties including high wear resistance, high workability, and thus suitable for use as collector material, lelectrical contact material or spring material, or the ike.

7 EXAMPLE 3 30% Fe 67% Cu 3% Al alloy 1. Melting conditions;

Voltage Current Slag Dia. of Size of composition. mold. electrode.

40 V 6200 A Ca F 150)? l50 mm. 70mm X 50mm Mg F,30% X length Al,0, 10%

2. Chemical composition of the alloy obtained: Cu Al Si Mn P S C Fe 66.5 3.l 0.02 0.08 0.005 0.007 0.0038 Bal -continued 3. The mechanical properties of the alloy obtained:

Material Tensile strength Elongation Hardness Kg/mm HRB Wire of 2.0 dia. 57.] l5.l 58

cold-drawn FIG. 10 represents a microstructure of the alloy obtained. The alloy not on] exhibited good mechanical properties including htg wear resistance but also showed high heat and corrosion resistances. Also It was found that the alloy could be hotand cold-worked satisfactory into sheets or wires.

What is claimed is:

l. A method of making iron-copper alloys having finely and umfonniy dispersed phase structure comprising the steps 0 forming a consumable electrode composed of a number of iron and copper wires positroned lengthwisel in an iron or copper ipe, compactmg the electrode y pressing it, the car said electrode beinghmited to less than 0.02 percent by weight, progressive y nciting the bottom end of said electrode by submerglng it in a molten slag containing at least one metal fluori e, and cooling the molten mass of metal formed from the consumable electrode.

2. A method as claimed in claim 1, including forming said consumable electrode to include aluminum wires of less than 3 percent by weight.

3. method as claimed in claim 1 and including forming said consumable electrode from rcent to 15 percent (by weight) iron and from l5 to 5 percent (by weight) copper.

A method as claimed in claim 1 where a set of iron wires and a set of copper wires are used in forming said electrode, and the wires of the two sets are mixed togregljier throughout the cross sectional area of the eleci l i i n content of 

1. A METHOD OF MAKING IRON-COPPER ALLOYS HAVING FINELY UNIFORMLY DISPERSED PHASE STRUCTURE COMPRISING THE STEPS OF FORMING A CONSUMABLE ELECTRODE COMPOSED OF A NUMBER OF IRON AND COPPER WIRES POSITIONED LENGTHWISELY IN AN IRON OR COPPER PIPE, COMPACTING THE ELECTRODE BY PRESSING IT, THE CARBON CONTENT OF SAID ELECTRODE BEING LIMITED TO LESS THAN 0.02 PERCENT BY WEIGHT PROGRESSIVELY MELTING THE BOTTOM END OF SAID ELECTRODE BY SUBMERGING IT IN A MOLTEN SLAG CONTAINING AT LEAST ONE METAL FLUORIDE, AND COOLING THE MOLTEN MASS OF METAL FORMED FROM THE CONSUMABLE ELECTRODE.
 2. A method as claimed in claim 1, including forming said consumable electrode to include aluminum wires of less than 3 percent by weight.
 3. A method as claimed in claim 1 and including forming said consumable electrode from 85 percent to 15 percent (by weight) iron and from 15 to 85 percent (by weight) copper.
 4. A method as claimed in claim 1 where a set of iron wires and a set of copper wires are used in forming said electrode, and the wires of the two sets are mixed together throughout the cross sectional area of the electrode. 